Method and apparatus for removing tread material from vehicle tires

ABSTRACT

A method and apparatus for removing tread material from vehicle tires preparatory to retreading the tire in which a rotary cutter rotating on an axis generally coplanar with the axis of rotation of the tire has sharp cutting elements therein which cut chips from the tread of the tire when the cutter and tire rotate relatively. The sharp cutting elements are formed of a hard wear resistant material such as cemented hard carbides and are detachably supported in a cutter body for ease of replacement therein and also so as to be indexable relative to the cutter body. The cutting elements, or inserts, have a high positive rake angle and the peripheries thereof are inclined at an angle slightly greater than the positive rake angle.

United States Patent Heaton et al.

1 i METHOD AND APPARATUS FOR REMOVING TREAD MATERIAL FROM VEHICLE TIRES[75] Inventors: James W. Heaton, Greensburg;

William E. Fawcett, Latrobe, both of Pa [73] Assignee: Kennametal lnc.,Latrobe, Pa.

[22] Filed: May 17, 1974 [21] Appl. No.: 471,050

Related [1.8. Application Data [63] Continuation of Ser. No. 379,372.July 16, 1973.

[52] US. Cl 82/1 C; 29/105 R; 157/13 [51] Int. Cl U B23b 3/00; B26d 1/12[58] Field of Search ..29/l05, 105 A, 78; 82/1 R, 82/1 C; 57/13 [56]References Cited UNITED STATES PATENTS 2,645,003 7/1953 Thompson et al.29/105 R 2,664,617 H1954 Kralowetz r r r 29/105 R 3,426,828 2/1969Neilsen 157/13 1 June 10, 1975 Primary ExaminerHarrison L HinsonAttorney, Agent, or Firm-Melvin A. Crosby [57] ABSTRACT A method andapparatus for removing tread material from vehicle tires preparatory toretreading the tire in which a rotary cutter rotating on an axisgenerally coplanar with the axis of rotation of the tire has sharpcutting elements therein which cut chips from the tread of the tire whenthe cutter and tire rotate relatively. The sharp cutting elements areformed of a hard wear resistant material such as cemented hard carbidesand are detachably supported in a cutter body for ease of replacementtherein and also so as to be indexable relative to the cutter body. Thecutting elements. or inserts, have a high positive rake angle and theperipheries thereof are inclined at an angle slightly greater than thepositive rake angle,

5 Claims, 6 Drawing Figures METHOD AND APPARATUS FOR REMOVING TREADMATERIAL FROM VEHICLE TIRES RELATED APPLICATION 1 James W. Heaton andWilliam E. Fawcett U.S. application Ser. No. 379.372, filed July lo.I973. for APPA- RATUS FOR REMOVING TRFAD MATERIAL FROM VEHICLE TIRES.

The present invention relates to the removing of tread material from avehicle tire preparatory to the retreading of the vehicle tire and isparticularly concerned with a method of removing the tread material andto a cutting device which effects the removal of the tread material fromthe tire.

This application is a continuation-in-part of Scr. No. 379.372. filedJuly In. I973. entitled Apparatus for Removing Tread Material FromVehicle Tires."

The removing of tread material from pneumatic vehi cle tires is a wellknown procedure and is generally accomplished by abrading the peripheryof the tire with an abrading element which may be in the form of abarbed rasp, or a moving member having coarse abrasive thereon. It hasalso been attempted to remove the tread material by cutting with a sharpknife.

The defect with the first mentioned system is that considerable heat isgenerated which results in the development of dust and smoke and vaporswhile. furthermore. the tread material is removed in such a manner thata great deal of it is in extremely fine form. thus,

creating a dusty condition which can be hazardous to the health andwhich can form a fire hazard and which, furthermore. requires theinstallation of rather expensive dust collecting equipment.

In the second mentioned method in which a sharp knife is employed forremoving the tread material. a

great deal of force is required to turn the tire against the cuttingblade and foreign material imbedded in the tread material can severelydamage such knives. Furthermore. this procedure for removing the treadmaterial from a vehicle tire is not as rapid as the removal of the treadmaterial by an abrasive device.

Having the foregoing in mind. a primary objective of the presentinvention is the provision of a method and apparatus for removing treadmaterial from a vehicle tire preparatory to retreading the tire which israpid and efficient.

Another object is the provision of a method and apparatus of the naturereferred to in which there is sub stantially no dust or smoke developedduring the removing of the material from the tire tread.

Still another object is the provision of a method and apparatus forremoving tread material from a vehicle tire preparatory to recapping thetire which eliminates the need for expensive dust separators and whichalso reduces health and fire hazards that usually go with such anoperation.

Still another object is the provision of a cutting device for cuttingtread rubber from a vehicle tire preparatory to recapping the tire inwhich replaceable indexable cutting elements are employed.

These and other objects and advantages of the present invention willbecome more apparent upon reference to the following detailedspecification taken in connection with the accompanying drawings inwhich:

FIG. 1 is a view illustrating diagrammatically a machine for use inremoving tread material from a vehicle inc.

FIG. 2 is a side view broken away and drawn at some what enlarged scaleshowing the cutting device used in the machine of FIG. I.

FIG. 3 is a section indicated on line IIIIII of FIG.

FIG. 4 is an exploded perspective view showing a cutting insert employedwith the cutting device of FIGS. 2 and 3 and showing the supporting nesttherefor and the clamp member which clamps the insert in the nest whilesimultaneously clamping the nest in a recess providcd therefor in thecutter body.

FIG. 5 is a schematic plan view showing how the cutting inserts could bestaggered laterally in the cutter body thereby to inhibit the formationof an irregular surface on the tire when the tread material is cuttherefrom.

FIG. 6 shows a modified type of cutting element or insert for use in thepractice of the invention.

BRIEF SUMMARY OF THE INVENTION According to the present invention, aspindle is provided on which a vehicle tire is mounted and inflated sothat the vehicle tire can be rotated on its axis while the tread portionthercofis firmly supported. Arranged in radially spaced relation to thetire and moveable ra dially toward and away from the tire is a cuttingdevice in the form of a disc-like body having detachably mounted thereinin circumferentially distributed rela tion a plurality of sharp edgedcutting elements, or inserts.

The cutting elements are individually replaceable and are individuallyindexable on the cutter body. The support for the cutter is alsorotatable about a vertical axis disposed near the region of the tread ofthe tire which is engaged by the cutter so that the cutter can be causedto follow a curved path across the tire tread thereby imparting thedesired shape thereto for receiving recapping material.

DETAILED DESCRIPTION OF THE INVENTION Referring to the drawings somewhatmore in detail, in FIG. 1, reference numeral 10 represents a spindleadapted for being driven in rotation by a motor MI and having means forsupporting a tire 12 which may be a conventional pneumatic vehicle tire.Tire I2 is a tire which is to be supplied with new tread material byknown recapping techniques and preparatory to having the new treadmaterial applied thereto. the old. worn tread material is cut away topresent a clean outwardly facing surface to which the new tread materialis caused to adhere by a vulcanization process.

The spindle 10 may be fixedly supported in any suitable machine framegenerally designated 14. The machine frame comprises a foot portion I6fixedly arranged relative to the portion supporting spindle 10 andhaving means defining a vertical pivot axis 18. Vertical pivot axis I8extends vertically in the region of the central radial plane of tire I2and somewhat radially inwardly from the outer periphery of tire I2.

Pivotally mounted on foot 16 so as to be swingable about axis 18 is anarm 20 on which there is slidably mounted a support 22. Support 22 isslidable radially toward and away from pivot axis I8 and. therefore,radially toward and away from tire I2. Support 22 carries a spindle 24drivingly connected to a motor M2 and mounted on spindle 24 is a cuttergenerally indicated at 26 which has distributed about the peripherysharp edged cutting elements.

When cutter 26 is driven in the direction of the arrow thereon andbrought into engagement with the periph cry of tire 12 when the tire isrotating in the direction of the arrow on the tire. the cutting insertsin the cutter will cut chips from the tire tread and in this mannerremove the desired amount of the worn tire tread.

By swinging arm about axis 18. the cutting of the tread can be caused toproceed over as much of the worn tread area as it is desired to remove.The cutting of the worn tread from the tire can be accomplished in asingle pass across the tire tread or in multiple passes. The support maybe cam controlled to produce the desired contour on the tire beingworked.

A particular point of novelty in respect of the device illustrated inH0. 1 is to be found in the cutter 26 which, as will be seen in F105. 2and 3. comprises a body 28 having a central aperture 30 for receivingspin dle 24. On the side of body 28 facing the spindle. the body isformed with notches 32 which receive keys 34 fixed to spindle 24. Thebody is clamped to the spindle by a large screw 36 threaded into thespindle and having a head engaging the bottom of recess 38 formed in theside of the cutter body facing away from the spindle.

The cutter body. as will best be seen in FIG. 2. has a plurality ofpockets or recesses 40 formed therein extending inwardly from theperiphery of the cutter body in uniformly distributed circumferentialrelation and each inclined in the same direction relative to the radialdirection of the body.

Each pocket or recess is adapted for receiving a nest member 42 whichhas a leg 44 at one side for engaging the adjacent side of the cutterbody 28. When a nest member 42 is inserted into a pocket until it abutsthe bottom wall of the pocket. and so that the leg 44 abuts one side ofthe cutter body, the respective nest element will be precisely locatedin its pocket.

Each nest element has a recess 46 formed therein and also has a pin 48extending into the recess. The recess is slightly more shallow in thedirection of the axis of pin 48 than the thickness of a cutting insert50 adapted for being received in the recess and the recess is likewiselarger in the radial direction of pin 48 than insert 50. The insert hasa central hole 52 which receives pin 48, and in this manner. the insertis located in the re cess and is likewise prevented from shiftingtherein.

As will be seen in FIG. 2, the one side of nest element 42 engages oneside of pocket 40 and the bottom wall of recess 46 which is formed inthe opposite side of the nest member. diverges in the radially outwarddirection with the opposite side of the nest member. The top face of aninsert 50 in the recess also diverges from the opposed side wall of thepocket in the outward direction.

Because of this. the cutting insert and nest member can be firmlyclamped in position by utilizing a simple wedge 54. the opposite sidesof which taper so that when one side of the wedge engages the adjacentside of a pocket 40, the opposite side of the wedge engages the exposedtop surface of the adjacent cutting insert 50.

The wedge 54 is adapted for being firmly drawn into pocket 40 to effectthe aforementioned wedging action by a screw 56 which has the oppositeends threaded in respectively opposite directions with the radiallyouter threaded end threadedly engaging a hole in the wedge and the otherthreaded end threadcdly engaging a threaded hole in the cutter bodywhich extends in a direction parallel to the wall of the pocket 40 andon which the wedge slides.

Each cutting element. or insert. 50 is formed of a hard wear resistantmaterial such as a good grade of tool steel or. preferably. a cementedhard metal carbide material such as tungsten or titanium carbide ormixtures thereof. Other hard metal carbides can be included in thecomposition without in any way detracting from the utility of theinserts.

As will best be seen in FIG. 4, each cutting element. or insert. 50 iscircular. has parallel top and bottom faces and a peripheral wall. Eachcutting element. or insert. can be indexed about the axis of therespective pin 48 so that when one peripheral portion of the element orinsert becomes worn. a new portion can be brought into cutting position.It will also be noted that the cutting element. or insert. has arelatively sharp edge 58 extending thereabout at the juncture of theperipheral wall with the top face with the included angle formed betweenthe peripheral wall and the top face ranging from about down to about30.

The included angle formed at the cutting edge is determined by the anglewhich the cutting clement makes with the peripheral surface of thecutter body adjacent thereto because the radially outer side of theperiphery ofthe cutting element must be inclined at such an angle as toprovide for clearance from the tread material being cut.

As illustrated in FIG. 2. each cutting element has an angle of about 45at the cutting edge and is inclined at an angle of about 30 to theradius so that the clearance angle at the radially outer side of theelement is on the order of about L5".

The insert of FIG. 6 has the cutting edge 47 reinforced by an axialportion 49 of peripheral wall 51 which makes a larger included anglewith the plane of top face 53 than does the axial portion 54 of theperipheral wall. Portion 49. for example. may make an angle of about 2to 5 less than the complement of the rake angle of the insert whileportion 54 makes a smaller angle with the plane of top face 53, up to45, for exam ple.

The cutter body may vary considerably in size and might be as small as 6inches or as large as l l /2 inches in diameter. The number of cuttingelements mounted in the cutters can vary from about 8 to about 12. Whenthe cutter is rotating on an axis parallel to that of the tire. thesmaller number of cutters is employed because, under these conditions.the maximum relative speed is obtained between the tread surface and thecutting elements in the cutter body.

When the tread is removed by the cutter rotating on an axis generallyperpendicular to the tire axis. a greater number of cutting elements aremounted in the cutter body. In both instances. the cutting elements areenabled to take cleanly cut chips of substantial size from the treadmaterial.

Each element might have a major diameter of about A to 1 inch and be onthe order of about /5 inch thick.

The particular cutting element illustrated in the drawings is circular.but it will be understood that the element could be polygonal whenviewed perpendicular to the top face thereof and still could be indexedabout the axis of symmetry thereof to present new cutting edgessuceessively to cutting position.

Inasmuch as tread material is somewhat resilient, there will be sometendency for the surface on the tire after the tread material has beencut off to be slightly irregular. This irregularity can be substantiallyreduced by using cutting elements having cutting edges parallel to theaxis of rotation of the cutter body or by making the cutter as indicatedin FIG. 5 wherein reference numeral 60 schematically illustrates thecutter body and shows how round button type cutting elements 62 could bemounted thereon in staggered relation thereby tending to eliminate theforming of objectionably large ridges on the surface of the tire beingcut.

in any case, the surface of the tire after having been cut off by acutter according to the present invention can be buffed and portions ofthe side wall of the tire adjacent the tread can also be buffed andthereby smooth the surface ofthe tire so that it is in ideal conditionfor receiving the retread material.

It has been discovered. however, that the clean smooth tread surfacewhich is left after a chip has been taken therefrom by a cutteraccording to the present invention, forms an ideal surface for receivingrecapping material and bonds to the recapping material more stronglythan does a conventional buffed surface which is obtained when a rasp isemployed to remove a tread.

Due to the sharp edges on the cutting elements. the tread material isremoved from the tire in the form of chips of substantial size and thecutting action is clean so that there is not much friction whereby aminimum amount of heat is developed and smoke and vapors are notgenerated during the cutting operation.

Furthermore, the material removed from the tire tread. as mentioned, isin the form of chips of substantial size and there is little or no dustdeveloped so that no dust collector need be employed when practicing thepresent invention. Also, since the chips are of substantial size, thefire hazard that would exist if fine dust were to be developed iseliminated as is also the health hazards that go with having the airladen with fine dust.

As an example of the speed of operation, a vehicle tire might bearranged to rotate at a surface speed of about Hit) up to more than1,000 feet per minute while the cutter might rotate at a peripheralspeed of about L000 up to 10,000 feet per minute with the tire surfaceand the cutter surface moving in respectively opposite directions.

The removal of the tread material from a conventional passenger vehicletire takes about 35 seconds when practicing the present invention, whichis less than the length of time required to remove the tread material byconventional methods using an abrasive tool which can take one minute ormore.

In locating the cutting elements or inserts on the rotatable cutter bodyand in correlating the speed of the tire being worked with the speed ofrotation of the cut ter body, it has been found that the best resultsare obtained when each cutting element on the cutter body removes a chipof substantial size from the tire tread. When the sharp edged cuttingelements take substantial chips from the tire tread. cleaner cuttingresults than is possible when a cutting element takes only a light cut.

The tread material is inherently yield-able and. unless each cuttingelement encounters a substantial body or rubber and takes a chipofsubstnntial size from the tire tread. there is a tendency for thetread to yield and to tear rather than to cut cleanly. Accordingly. itwill be understood that, in the practice of the present invention, eachcutting element is intended to remove a clean chip of substantial sizefrom the tread material Normally, a single pass across a tire tread isample for removing the desired amount of tread material and, with eachcutting element taking a clean chip with a clean cut from the treadmaterial, the end result is a surface ideally adapted for bonding torecapping material.

Tests and experiments have shown that the bonding of the recappingmaterial to the tread material of a tire which has been cut with acutter device according to the present invention is as strong and up to50 percent stronger, for example, than the strength of the bond whichexists between retreading or recapping material and a tread surfacewhich has been prepared by buffing with a rasp or the like.

it is also important for the clearance angle behind each cutting edge tobe at least equal to and. preferably, slightly greater than the positiverake angle on the front side of each cutting insert because this assistsin making a clean cut and prevents the cutting inserts from rubbing onthe tread material and developing heat therein. A tire from which thetread has been removed by the use ofa cutting device according to thepresent invention exhibits substantially no rise in temperature duringthe cutting operation and, similarly, the cutting elements also remaincool during the cutting operation.

it will be noted that the cutter body has a wedge shape in cross sectionat the periphery and this is done to provide support for the cuttingelement or insert on the rearward side as near as possible to theradially outer extremity thereof. it will also be noted that the wedgein front of each insert is arcuately recessed across the radially outerend to provide guidance and clearance for the large chips taken by theinserts.

In order to insure the taking of cleanly cut chips of substantial sizefrom the tire tread. the cutting elements, or inserts, are spaced in thedirection of movement thereof a substantial distance, for example, adistance of about four inches between each insert, and the nestfollowing insert has been found to be sufficient to cause each insert toencounter a substantial body of tread material when moving past the tiretread and. therefore, to cause each insert to take a cleanly cut chip ofsubstantial size from the tread of the tire.

The cutter body and the tire are shown as rotating on parallel axes, butit is possible for the axes of the tire and the cutter body to beperpendicular to each other. In either case, the cutter body traversesthe tire tread during cutting and follows an arcuate path across thecrown of the tire and moves radially inwardly at each side of the tiretread for a distance sufficient to prepare the tire to receive therecapping material.

Modifications may be made within the scope of the appended claims.

What is claimed is:

l. The method of removing the tread material from a pneumatic tirepreparatory to recapping thereof which comprises; inflating the tire,rotating the inflated tire on the axis thereof, mounting hard wearresistant circular cutting elements in circumferentially spaced andaxially coplanar relation in a holder with each insert having a sharpperipheral edge protruding radially from the holder, presenting theholder to the tread of the tire with the axis of the holder parallel tothe axis of the tire and with the inserts at a positive rake angle of atleast about moving the holder with the inserts therein relatively to thetire. and feeding the holder and tire relatively in the radial and axialdirections of the tire to cause each insert to take cleanly cut chips ofsubstantial size from the tire tread whereby the said inserts form aplurality of circumferentially and axially distributed shallow groovesin the tire tread.

2. The method according to claim 1 in which said chips are ofsubstantial thickness 3. The method according to claim 1 in which saidholder rotates at a surface speed of about 10000 feet is on the order ofabout 4 inches.

1. The method of removing the tread material from a pneumatic tire preparatory to recapping thereof which comprises; inflating the tire, rotating the inflated tire on the axis thereof, mounting hard wear resistant circular cutting elements in circumferentially spaced and axially coplanar relation in a holder with each insert having a sharp peripheral edge protruding radially from the holder, presenting the holder to the tread of the tire with the axis of the holder parallel to the axis of the tire and with the inserts at a positive rake angle of at least about 25*, moving the holder with the inserts therein relatively to the tire, and feeding the holder and tire relatively in the radial and axial directions of the tire to cause each insert to take cleanly cut chips of substantial size from the tire tread whereby the said inserts form a plurality of circumferentially and axially distributed shallow grooves in the tire tread.
 2. The method according to claim 1 in which said chips are of substantial thickness.
 3. The method according to claim 1 in which said holder rotates at a surface speed of about 10,000 feet per minute and said tire rotates at a surface speed of about 1,000 feet per minute.
 4. The method according to claim 3 in which the inserts are spaced in the direction of movement thereof a distance such that each insert engages a substantial body of tread material each time the insert moves past the tire tread.
 5. The method according to claim 4 in which said distance between each insert and the next following insert is on the order of about 4 inches. 